src/hb-ot-cmap-table.hh

/*
 * Copyright © 2014  Google, Inc.
 *
 *  This is part of HarfBuzz, a text shaping library.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Google Author(s): Behdad Esfahbod
 */

#ifndef HB_OT_CMAP_TABLE_HH
#define HB_OT_CMAP_TABLE_HH

#include "hb-open-type.hh"
#include "hb-set.hh"

/*
 * cmap -- Character to Glyph Index Mapping
 * https://docs.microsoft.com/en-us/typography/opentype/spec/cmap
 */
#define HB_OT_TAG_cmap HB_TAG('c','m','a','p')

namespace OT {


struct CmapSubtableFormat0
{
  bool get_glyph (hb_codepoint_t codepoint, hb_codepoint_t *glyph) const
  {
    hb_codepoint_t gid = codepoint < 256 ? glyphIdArray[codepoint] : 0;
    if (!gid)
      return false;
    *glyph = gid;
    return true;
  }
  void collect_unicodes (hb_set_t *out) const
  {
    for (unsigned int i = 0; i < 256; i++)
      if (glyphIdArray[i])
	out->add (i);
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  protected:
  HBUINT16	format;		/* Format number is set to 0. */
  HBUINT16	length;		/* Byte length of this subtable. */
  HBUINT16	language;	/* Ignore. */
  HBUINT8	glyphIdArray[256];/* An array that maps character
				 * code to glyph index values. */
  public:
  DEFINE_SIZE_STATIC (6 + 256);
};

struct CmapSubtableFormat4
{

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  HBUINT16* serialize_endcode_array (hb_serialize_context_t *c,
                                     Iterator it)
  {
    HBUINT16 *endCode = c->start_embed<HBUINT16> ();
    hb_codepoint_t prev_endcp = 0xFFFF;

    + it
    | hb_apply ([&] (const hb_item_type<Iterator> _)
                {
                  if (prev_endcp != 0xFFFF && prev_endcp + 1u != _.first)
                  {
                    HBUINT16 end_code;
                    end_code = prev_endcp;
                    c->copy<HBUINT16> (end_code);
                  }
                  prev_endcp = _.first;
                })
    ;

    {
      // last endCode
      HBUINT16 endcode;
      endcode = prev_endcp;
      if (unlikely (!c->copy<HBUINT16> (endcode))) return nullptr;
      // There must be a final entry with end_code == 0xFFFF.
      if (prev_endcp != 0xFFFF)
      {
        HBUINT16 finalcode;
        finalcode = 0xFFFF;
        if (unlikely (!c->copy<HBUINT16> (finalcode))) return nullptr;
      }
    }

    return endCode;
  }

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  HBUINT16* serialize_startcode_array (hb_serialize_context_t *c,
                                       Iterator it)
  {
    HBUINT16 *startCode = c->start_embed<HBUINT16> ();
    hb_codepoint_t prev_cp = 0xFFFF;
    
    + it
    | hb_apply ([&] (const hb_item_type<Iterator> _)
                {
                  if (prev_cp == 0xFFFF || prev_cp + 1u != _.first)
                  {
                    HBUINT16 start_code;
                    start_code = _.first;
                    c->copy<HBUINT16> (start_code);
                  }

                  prev_cp = _.first;
                })
    ;

    // There must be a final entry with end_code == 0xFFFF.
    if (it.len () == 0 || prev_cp != 0xFFFF)
    {
      HBUINT16 finalcode;
      finalcode = 0xFFFF;
      if (unlikely (!c->copy<HBUINT16> (finalcode))) return nullptr;
    }

    return startCode;
  }

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  HBINT16* serialize_idDelta_array (hb_serialize_context_t *c,
                                     Iterator it,
                                     HBUINT16 *endCode,
                                     HBUINT16 *startCode,
                                     unsigned segcount)
  {
    unsigned i = 0;
    hb_codepoint_t last_gid = 0, start_gid = 0, last_cp = 0xFFFF;
    bool use_delta = true;
    
    HBINT16 *idDelta = c->start_embed<HBINT16> ();
    if ((char *)idDelta - (char *)startCode != (int) segcount * (int) HBINT16::static_size)
      return nullptr;

    + it
    | hb_apply ([&] (const hb_item_type<Iterator> _)
                {
                  if (_.first == startCode[i])
                  {
                    use_delta = true;
                    start_gid = _.second;
                  }
                  else if (_.second != last_gid + 1) use_delta = false;

                  if (_.first == endCode[i])
                  {
                    HBINT16 delta;
                    if (use_delta) delta = (int)start_gid - (int)startCode[i];
                    else delta = 0;
                    c->copy<HBINT16> (delta);

                    i++;
                  }

                  last_gid = _.second;
                  last_cp = _.first;
                })
    ;

    if (it.len () == 0 || last_cp != 0xFFFF)
    {
      HBINT16 delta;
      delta = 1;
      if (unlikely (!c->copy<HBINT16> (delta))) return nullptr;
    }

    return idDelta;
  }

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  HBUINT16* serialize_rangeoffset_glyid (hb_serialize_context_t *c,
                                     Iterator it,
                                     HBUINT16 *endCode,
                                     HBUINT16 *startCode,
                                     HBINT16 *idDelta,
                                     unsigned segcount)
  {
    HBUINT16 *idRangeOffset = c->allocate_size<HBUINT16> (HBUINT16::static_size * segcount);
    if (unlikely (!c->check_success (idRangeOffset))) return nullptr;
    if (unlikely ((char *)idRangeOffset - (char *)idDelta != (int) segcount * (int) HBINT16::static_size)) return nullptr;
 
    + hb_range (segcount)
    | hb_filter ([&] (const unsigned _) { return idDelta[_] == 0; })
    | hb_apply ([&] (const unsigned i)
                {
                  idRangeOffset[i] = 2 * (c->start_embed<HBUINT16> () - idRangeOffset - i);

                  + it
                  | hb_filter ([&] (const hb_item_type<Iterator> _) { return _.first >= startCode[i] && _.first <= endCode[i]; })
                  | hb_apply ([&] (const hb_item_type<Iterator> _)
                              {
                                HBUINT16 glyID;
                                glyID = _.second;
                                c->copy<HBUINT16> (glyID);
                              })
                  ;


                })
    ;

    return idRangeOffset;
  }

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  void serialize (hb_serialize_context_t *c,
		  Iterator it)
  {
    unsigned table_initpos = c->length ();
    if (unlikely (!c->extend_min (*this))) return;
    this->format = 4;

    //serialize endCode[]
    HBUINT16 *endCode = serialize_endcode_array (c, it);
    if (unlikely (!endCode)) return;

    unsigned segcount = (c->length () - min_size) / HBUINT16::static_size;
    
    // 2 bytes of padding.
    if (unlikely (!c->allocate_size<HBUINT16> (HBUINT16::static_size))) return; // 2 bytes of padding.

   // serialize startCode[]
    HBUINT16 *startCode = serialize_startcode_array (c, it);
    if (unlikely (!startCode)) return;
    
    //serialize idDelta[]
    HBINT16 *idDelta = serialize_idDelta_array (c, it, endCode, startCode, segcount);
    if (unlikely (!idDelta)) return;

    HBUINT16 *idRangeOffset = serialize_rangeoffset_glyid (c, it, endCode, startCode, idDelta, segcount);
    if (unlikely (!c->check_success (idRangeOffset))) return;
 
    if (unlikely (!c->check_assign(this->length, c->length () - table_initpos))) return;
    this->segCountX2 = segcount * 2;
    this->entrySelector = hb_max (1u, hb_bit_storage (segcount)) - 1;
    this->searchRange = 2 * (1u << this->entrySelector);
    this->rangeShift = segcount * 2 > this->searchRange
		       ? 2 * segcount - this->searchRange
		       : 0;
  }

  struct accelerator_t
  {
    accelerator_t () {}
    accelerator_t (const CmapSubtableFormat4 *subtable) { init (subtable); }
    ~accelerator_t () { fini (); }

    void init (const CmapSubtableFormat4 *subtable)
    {
      segCount = subtable->segCountX2 / 2;
      endCount = subtable->values.arrayZ;
      startCount = endCount + segCount + 1;
      idDelta = startCount + segCount;
      idRangeOffset = idDelta + segCount;
      glyphIdArray = idRangeOffset + segCount;
      glyphIdArrayLength = (subtable->length - 16 - 8 * segCount) / 2;
    }
    void fini () {}

    bool get_glyph (hb_codepoint_t codepoint, hb_codepoint_t *glyph) const
    {
      /* Custom two-array bsearch. */
      int min = 0, max = (int) this->segCount - 1;
      const HBUINT16 *startCount = this->startCount;
      const HBUINT16 *endCount = this->endCount;
      unsigned int i;
      while (min <= max)
      {
	int mid = ((unsigned int) min + (unsigned int) max) / 2;
	if (codepoint < startCount[mid])
	  max = mid - 1;
	else if (codepoint > endCount[mid])
	  min = mid + 1;
	else
	{
	  i = mid;
	  goto found;
	}
      }
      return false;

    found:
      hb_codepoint_t gid;
      unsigned int rangeOffset = this->idRangeOffset[i];
      if (rangeOffset == 0)
	gid = codepoint + this->idDelta[i];
      else
      {
	/* Somebody has been smoking... */
	unsigned int index = rangeOffset / 2 + (codepoint - this->startCount[i]) + i - this->segCount;
	if (unlikely (index >= this->glyphIdArrayLength))
	  return false;
	gid = this->glyphIdArray[index];
	if (unlikely (!gid))
	  return false;
	gid += this->idDelta[i];
      }
      gid &= 0xFFFFu;
      if (!gid)
	return false;
      *glyph = gid;
      return true;
    }
    HB_INTERNAL static bool get_glyph_func (const void *obj, hb_codepoint_t codepoint, hb_codepoint_t *glyph)
    {
      return ((const accelerator_t *) obj)->get_glyph (codepoint, glyph);
    }
    void collect_unicodes (hb_set_t *out) const
    {
      unsigned int count = this->segCount;
      if (count && this->startCount[count - 1] == 0xFFFFu)
	count--; /* Skip sentinel segment. */
      for (unsigned int i = 0; i < count; i++)
      {
	unsigned int rangeOffset = this->idRangeOffset[i];
	if (rangeOffset == 0)
	  out->add_range (this->startCount[i], this->endCount[i]);
	else
	{
	  for (hb_codepoint_t codepoint = this->startCount[i];
	       codepoint <= this->endCount[i];
	       codepoint++)
	  {
	    unsigned int index = rangeOffset / 2 + (codepoint - this->startCount[i]) + i - this->segCount;
	    if (unlikely (index >= this->glyphIdArrayLength))
	      break;
	    hb_codepoint_t gid = this->glyphIdArray[index];
	    if (unlikely (!gid))
	      continue;
	    out->add (codepoint);
	  }
	}
      }
    }

    const HBUINT16 *endCount;
    const HBUINT16 *startCount;
    const HBUINT16 *idDelta;
    const HBUINT16 *idRangeOffset;
    const HBUINT16 *glyphIdArray;
    unsigned int segCount;
    unsigned int glyphIdArrayLength;
  };

  bool get_glyph (hb_codepoint_t codepoint, hb_codepoint_t *glyph) const
  {
    accelerator_t accel (this);
    return accel.get_glyph_func (&accel, codepoint, glyph);
  }
  void collect_unicodes (hb_set_t *out) const
  {
    accelerator_t accel (this);
    accel.collect_unicodes (out);
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (unlikely (!c->check_struct (this)))
      return_trace (false);

    if (unlikely (!c->check_range (this, length)))
    {
      /* Some broken fonts have too long of a "length" value.
       * If that is the case, just change the value to truncate
       * the subtable at the end of the blob. */
      uint16_t new_length = (uint16_t) hb_min ((uintptr_t) 65535,
					    (uintptr_t) (c->end -
							 (char *) this));
      if (!c->try_set (&length, new_length))
	return_trace (false);
    }

    return_trace (16 + 4 * (unsigned int) segCountX2 <= length);
  }



  protected:
  HBUINT16	format;		/* Format number is set to 4. */
  HBUINT16	length;		/* This is the length in bytes of the
				 * subtable. */
  HBUINT16	language;	/* Ignore. */
  HBUINT16	segCountX2;	/* 2 x segCount. */
  HBUINT16	searchRange;	/* 2 * (2**floor(log2(segCount))) */
  HBUINT16	entrySelector;	/* log2(searchRange/2) */
  HBUINT16	rangeShift;	/* 2 x segCount - searchRange */

  UnsizedArrayOf<HBUINT16>
		values;
#if 0
  HBUINT16	endCount[segCount];	/* End characterCode for each segment,
					 * last=0xFFFFu. */
  HBUINT16	reservedPad;		/* Set to 0. */
  HBUINT16	startCount[segCount];	/* Start character code for each segment. */
  HBINT16		idDelta[segCount];	/* Delta for all character codes in segment. */
  HBUINT16	idRangeOffset[segCount];/* Offsets into glyphIdArray or 0 */
  UnsizedArrayOf<HBUINT16>
		glyphIdArray;	/* Glyph index array (arbitrary length) */
#endif

  public:
  DEFINE_SIZE_ARRAY (14, values);
};

struct CmapSubtableLongGroup
{
  friend struct CmapSubtableFormat12;
  friend struct CmapSubtableFormat13;
  template<typename U>
  friend struct CmapSubtableLongSegmented;
  friend struct cmap;

  int cmp (hb_codepoint_t codepoint) const
  {
    if (codepoint < startCharCode) return -1;
    if (codepoint > endCharCode)   return +1;
    return 0;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  private:
  HBUINT32		startCharCode;	/* First character code in this group. */
  HBUINT32		endCharCode;	/* Last character code in this group. */
  HBUINT32		glyphID;	/* Glyph index; interpretation depends on
					 * subtable format. */
  public:
  DEFINE_SIZE_STATIC (12);
};
DECLARE_NULL_NAMESPACE_BYTES (OT, CmapSubtableLongGroup);

template <typename UINT>
struct CmapSubtableTrimmed
{
  bool get_glyph (hb_codepoint_t codepoint, hb_codepoint_t *glyph) const
  {
    /* Rely on our implicit array bound-checking. */
    hb_codepoint_t gid = glyphIdArray[codepoint - startCharCode];
    if (!gid)
      return false;
    *glyph = gid;
    return true;
  }
  void collect_unicodes (hb_set_t *out) const
  {
    hb_codepoint_t start = startCharCode;
    unsigned int count = glyphIdArray.len;
    for (unsigned int i = 0; i < count; i++)
      if (glyphIdArray[i])
	out->add (start + i);
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && glyphIdArray.sanitize (c));
  }

  protected:
  UINT		formatReserved;	/* Subtable format and (maybe) padding. */
  UINT		length;		/* Byte length of this subtable. */
  UINT		language;	/* Ignore. */
  UINT		startCharCode;	/* First character code covered. */
  ArrayOf<GlyphID, UINT>
		glyphIdArray;	/* Array of glyph index values for character
				 * codes in the range. */
  public:
  DEFINE_SIZE_ARRAY (5 * sizeof (UINT), glyphIdArray);
};

struct CmapSubtableFormat6  : CmapSubtableTrimmed<HBUINT16> {};
struct CmapSubtableFormat10 : CmapSubtableTrimmed<HBUINT32 > {};

template <typename T>
struct CmapSubtableLongSegmented
{
  friend struct cmap;

  bool get_glyph (hb_codepoint_t codepoint, hb_codepoint_t *glyph) const
  {
    hb_codepoint_t gid = T::group_get_glyph (groups.bsearch (codepoint), codepoint);
    if (!gid)
      return false;
    *glyph = gid;
    return true;
  }

  void collect_unicodes (hb_set_t *out) const
  {
    for (unsigned int i = 0; i < this->groups.len; i++) {
      out->add_range (this->groups[i].startCharCode,
		      hb_min ((hb_codepoint_t) this->groups[i].endCharCode,
			   (hb_codepoint_t) HB_UNICODE_MAX));
    }
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && groups.sanitize (c));
  }

  protected:
  HBUINT16	format;		/* Subtable format; set to 12. */
  HBUINT16	reserved;	/* Reserved; set to 0. */
  HBUINT32	length;		/* Byte length of this subtable. */
  HBUINT32	language;	/* Ignore. */
  SortedArrayOf<CmapSubtableLongGroup, HBUINT32>
		groups;		/* Groupings. */
  public:
  DEFINE_SIZE_ARRAY (16, groups);
};

struct CmapSubtableFormat12 : CmapSubtableLongSegmented<CmapSubtableFormat12>
{
  static hb_codepoint_t group_get_glyph (const CmapSubtableLongGroup &group,
					 hb_codepoint_t u)
  { return likely (group.startCharCode <= group.endCharCode) ?
	   group.glyphID + (u - group.startCharCode) : 0; }


  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  void serialize (hb_serialize_context_t *c,
		  Iterator it)
  {
    if (it.len () == 0) return;
    unsigned table_initpos = c->length ();
    if (unlikely (!c->extend_min (*this))) return;

    hb_codepoint_t startCharCode = 0xFFFF, endCharCode = 0xFFFF;
    hb_codepoint_t glyphID = 0;

    + it
    | hb_apply ([&] (const hb_item_type<Iterator> _)
              {
                if (startCharCode == 0xFFFF)
                {
                  startCharCode = _.first;
                  endCharCode = _.first;
                  glyphID = _.second;
                }
                else if (!_is_gid_consecutive (endCharCode, startCharCode, glyphID, _.first, _.second))
                {
                  CmapSubtableLongGroup  grouprecord;
                  grouprecord.startCharCode = startCharCode;
                  grouprecord.endCharCode = endCharCode;
                  grouprecord.glyphID = glyphID;
                  c->copy<CmapSubtableLongGroup> (grouprecord);

                  startCharCode = _.first;
                  endCharCode = _.first;
                  glyphID = _.second;
                }
                else
                {
                  endCharCode = _.first;
                }
              })
    ;

    CmapSubtableLongGroup record;
    record.startCharCode = startCharCode;
    record.endCharCode = endCharCode;
    record.glyphID = glyphID;
    c->copy<CmapSubtableLongGroup> (record);

    this->format = 12;
    this->reserved = 0;
    this->length = c->length () - table_initpos;
    this->groups.len = (this->length - min_size)/CmapSubtableLongGroup::static_size;
  }

  static size_t get_sub_table_size (const hb_sorted_vector_t<CmapSubtableLongGroup> &groups_data)
  {
    return 16 + 12 * groups_data.length;
  }

 private:
  static bool _is_gid_consecutive (hb_codepoint_t endCharCode,
                                   hb_codepoint_t startCharCode,
                                   hb_codepoint_t glyphID,
				   hb_codepoint_t cp,
				   hb_codepoint_t new_gid)
  {
    return (cp - 1 == endCharCode) &&
	new_gid == glyphID + (cp - startCharCode);
  }

};

struct CmapSubtableFormat13 : CmapSubtableLongSegmented<CmapSubtableFormat13>
{
  static hb_codepoint_t group_get_glyph (const CmapSubtableLongGroup &group,
					 hb_codepoint_t u HB_UNUSED)
  { return group.glyphID; }
};

typedef enum
{
  GLYPH_VARIANT_NOT_FOUND = 0,
  GLYPH_VARIANT_FOUND = 1,
  GLYPH_VARIANT_USE_DEFAULT = 2
} glyph_variant_t;

struct UnicodeValueRange
{
  int cmp (const hb_codepoint_t &codepoint) const
  {
    if (codepoint < startUnicodeValue) return -1;
    if (codepoint > startUnicodeValue + additionalCount) return +1;
    return 0;
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  HBUINT24	startUnicodeValue;	/* First value in this range. */
  HBUINT8	additionalCount;	/* Number of additional values in this
					 * range. */
  public:
  DEFINE_SIZE_STATIC (4);
};

struct DefaultUVS : SortedArrayOf<UnicodeValueRange, HBUINT32>
{
  void collect_unicodes (hb_set_t *out) const
  {
    unsigned int count = len;
    for (unsigned int i = 0; i < count; i++)
    {
      hb_codepoint_t first = arrayZ[i].startUnicodeValue;
      hb_codepoint_t last = hb_min ((hb_codepoint_t) (first + arrayZ[i].additionalCount),
				 (hb_codepoint_t) HB_UNICODE_MAX);
      out->add_range (first, last);
    }
  }

  public:
  DEFINE_SIZE_ARRAY (4, *this);
};

struct UVSMapping
{
  int cmp (const hb_codepoint_t &codepoint) const
  {
    return unicodeValue.cmp (codepoint);
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  HBUINT24	unicodeValue;	/* Base Unicode value of the UVS */
  GlyphID	glyphID;	/* Glyph ID of the UVS */
  public:
  DEFINE_SIZE_STATIC (5);
};

struct NonDefaultUVS : SortedArrayOf<UVSMapping, HBUINT32>
{
  void collect_unicodes (hb_set_t *out) const
  {
    unsigned int count = len;
    for (unsigned int i = 0; i < count; i++)
      out->add (arrayZ[i].glyphID);
  }

  public:
  DEFINE_SIZE_ARRAY (4, *this);
};

struct VariationSelectorRecord
{
  glyph_variant_t get_glyph (hb_codepoint_t codepoint,
			     hb_codepoint_t *glyph,
			     const void *base) const
  {
    if ((base+defaultUVS).bfind (codepoint))
      return GLYPH_VARIANT_USE_DEFAULT;
    const UVSMapping &nonDefault = (base+nonDefaultUVS).bsearch (codepoint);
    if (nonDefault.glyphID)
    {
      *glyph = nonDefault.glyphID;
       return GLYPH_VARIANT_FOUND;
    }
    return GLYPH_VARIANT_NOT_FOUND;
  }

  void collect_unicodes (hb_set_t *out, const void *base) const
  {
    (base+defaultUVS).collect_unicodes (out);
    (base+nonDefaultUVS).collect_unicodes (out);
  }

  int cmp (const hb_codepoint_t &variation_selector) const
  {
    return varSelector.cmp (variation_selector);
  }

  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
		  defaultUVS.sanitize (c, base) &&
		  nonDefaultUVS.sanitize (c, base));
  }

  HBUINT24	varSelector;	/* Variation selector. */
  LOffsetTo<DefaultUVS>
		defaultUVS;	/* Offset to Default UVS Table.  May be 0. */
  LOffsetTo<NonDefaultUVS>
		nonDefaultUVS;	/* Offset to Non-Default UVS Table.  May be 0. */
  public:
  DEFINE_SIZE_STATIC (11);
};

struct CmapSubtableFormat14
{
  glyph_variant_t get_glyph_variant (hb_codepoint_t codepoint,
				     hb_codepoint_t variation_selector,
				     hb_codepoint_t *glyph) const
  {
    return record.bsearch (variation_selector).get_glyph (codepoint, glyph, this);
  }

  void collect_variation_selectors (hb_set_t *out) const
  {
    unsigned int count = record.len;
    for (unsigned int i = 0; i < count; i++)
      out->add (record.arrayZ[i].varSelector);
  }
  void collect_variation_unicodes (hb_codepoint_t variation_selector,
				   hb_set_t *out) const
  {
    record.bsearch (variation_selector).collect_unicodes (out, this);
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
		  record.sanitize (c, this));
  }

  protected:
  HBUINT16	format;		/* Format number is set to 14. */
  HBUINT32	length;		/* Byte length of this subtable. */
  SortedArrayOf<VariationSelectorRecord, HBUINT32>
		record;		/* Variation selector records; sorted
				 * in increasing order of `varSelector'. */
  public:
  DEFINE_SIZE_ARRAY (10, record);
};

struct CmapSubtable
{
  /* Note: We intentionally do NOT implement subtable formats 2 and 8. */

  bool get_glyph (hb_codepoint_t codepoint,
		  hb_codepoint_t *glyph) const
  {
    switch (u.format) {
    case  0: return u.format0 .get_glyph (codepoint, glyph);
    case  4: return u.format4 .get_glyph (codepoint, glyph);
    case  6: return u.format6 .get_glyph (codepoint, glyph);
    case 10: return u.format10.get_glyph (codepoint, glyph);
    case 12: return u.format12.get_glyph (codepoint, glyph);
    case 13: return u.format13.get_glyph (codepoint, glyph);
    case 14:
    default: return false;
    }
  }
  void collect_unicodes (hb_set_t *out) const
  {
    switch (u.format) {
    case  0: u.format0 .collect_unicodes (out); return;
    case  4: u.format4 .collect_unicodes (out); return;
    case  6: u.format6 .collect_unicodes (out); return;
    case 10: u.format10.collect_unicodes (out); return;
    case 12: u.format12.collect_unicodes (out); return;
    case 13: u.format13.collect_unicodes (out); return;
    case 14:
    default: return;
    }
  }

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  void serialize (hb_serialize_context_t *c,
		  Iterator it,
                  unsigned format)
  {
    switch (format) {
    case  4: u.format4.serialize (c, it);  return;
    case 12: u.format12.serialize (c, it); return;
    default: return;
    }
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (!u.format.sanitize (c)) return_trace (false);
    switch (u.format) {
    case  0: return_trace (u.format0 .sanitize (c));
    case  4: return_trace (u.format4 .sanitize (c));
    case  6: return_trace (u.format6 .sanitize (c));
    case 10: return_trace (u.format10.sanitize (c));
    case 12: return_trace (u.format12.sanitize (c));
    case 13: return_trace (u.format13.sanitize (c));
    case 14: return_trace (u.format14.sanitize (c));
    default:return_trace (true);
    }
  }

  public:
  union {
  HBUINT16		format;		/* Format identifier */
  CmapSubtableFormat0	format0;
  CmapSubtableFormat4	format4;
  CmapSubtableFormat6	format6;
  CmapSubtableFormat10	format10;
  CmapSubtableFormat12	format12;
  CmapSubtableFormat13	format13;
  CmapSubtableFormat14	format14;
  } u;
  public:
  DEFINE_SIZE_UNION (2, format);
};


struct EncodingRecord
{
  int cmp (const EncodingRecord &other) const
  {
    int ret;
    ret = platformID.cmp (other.platformID);
    if (ret) return ret;
    ret = encodingID.cmp (other.encodingID);
    if (ret) return ret;
    return 0;
  }

  bool sanitize (hb_sanitize_context_t *c, const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
		  subtable.sanitize (c, base));
  }

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  EncodingRecord* copy (hb_serialize_context_t *c,
                        Iterator it,
                        unsigned format,
                        void *base,
                        /* INOUT */ unsigned *objidx) const
  {
    TRACE_SERIALIZE (this);
    auto *out = c->embed (this);
    if (unlikely (!out)) return_trace (nullptr);
    out->subtable = 0;

    if (*objidx == 0)
    {
      CmapSubtable *cmapsubtable = c->push<CmapSubtable> ();
      unsigned origin_length = c->length ();
      cmapsubtable->serialize (c, it, format);
      if (c->length () - origin_length > 0) *objidx = c->pop_pack ();
      else c->pop_discard ();
    }

    c->add_link (out->subtable, *objidx, base);
    return_trace (out);
  }

  HBUINT16	platformID;	/* Platform ID. */
  HBUINT16	encodingID;	/* Platform-specific encoding ID. */
  LOffsetTo<CmapSubtable>
		subtable;	/* Byte offset from beginning of table to the subtable for this encoding. */
  public:
  DEFINE_SIZE_STATIC (8);
};

struct cmap
{
  static constexpr hb_tag_t tableTag = HB_OT_TAG_cmap;

  template<typename Iterator,
           hb_requires (hb_is_iterator (Iterator))>
  void serialize (hb_serialize_context_t *c,
                  Iterator it,
                  const EncodingRecord *unicode_bmp,
                  const EncodingRecord *unicode_ucs4,
                  const EncodingRecord *ms_bmp,
                  const EncodingRecord *ms_ucs4)
  {
    if (unlikely (!c->extend_min ((*this))))  return;
    this->version = 0;

    unsigned numTables = (unicode_bmp ? 1 : 0) + (unicode_ucs4 ? 1 : 0) + (ms_bmp ? 1 : 0) + (ms_ucs4 ? 1 : 0);
    if (unlikely (!c->check_assign(this->encodingRecord.len, numTables))) return;

    unsigned format4objidx = 0, format12objidx = 0;
    if (unicode_bmp) c->copy (unicode_bmp, it, 4u, this, &format4objidx);
    if (unicode_ucs4) c->copy (unicode_ucs4, it, 12u, this, &format12objidx);
    if (ms_bmp) c->copy (ms_bmp, it, 4u, this, &format4objidx);
    if (ms_ucs4) c->copy (ms_ucs4, it, 12u, this, &format12objidx);

  }

  bool subset (hb_subset_context_t *c) const
  {
    TRACE_SUBSET (this);

    cmap *cmap_prime = c->serializer->start_embed<cmap> ();
    if (unlikely (!c->serializer->check_success (cmap_prime))) return_trace (false);

    const EncodingRecord *unicode_bmp = find_encodingrec (0, 3);
    const EncodingRecord *unicode_ucs4 = find_encodingrec (0, 4);
    const EncodingRecord *ms_bmp = find_encodingrec (3, 1);
    const EncodingRecord *ms_ucs4 = find_encodingrec (3, 10);
    bool has_format12 = find_subtable (12);

    if (unlikely (!unicode_bmp && !ms_bmp)) return_trace (false);
    if (unlikely (has_format12 && (!unicode_ucs4 && !ms_ucs4))) return_trace (false);


    auto it =
    + hb_iter (c->plan->unicodes)
    | hb_map ([&] (hb_codepoint_t _)
                 {
                   hb_codepoint_t new_gid = HB_MAP_VALUE_INVALID;
                   c->plan->new_gid_for_codepoint (_, &new_gid);
                   return hb_pair_t<hb_codepoint_t, hb_codepoint_t> (_, new_gid);
                 })
    | hb_filter ([&] (const hb_pair_t<hb_codepoint_t, hb_codepoint_t> _)
              {
                return (_.second != HB_MAP_VALUE_INVALID);
              })
    ;

    cmap_prime->serialize (c->serializer, it, unicode_bmp, unicode_ucs4, ms_bmp, ms_ucs4);
    return_trace (true);
  }

  const CmapSubtable *find_best_subtable (bool *symbol = nullptr) const
  {
    if (symbol) *symbol = false;

    const CmapSubtable *subtable;

    /* 32-bit subtables. */
    if ((subtable = this->find_subtable (3, 10))) return subtable;
    if ((subtable = this->find_subtable (0, 6))) return subtable;
    if ((subtable = this->find_subtable (0, 4))) return subtable;

    /* 16-bit subtables. */
    if ((subtable = this->find_subtable (3, 1))) return subtable;
    if ((subtable = this->find_subtable (0, 3))) return subtable;
    if ((subtable = this->find_subtable (0, 2))) return subtable;
    if ((subtable = this->find_subtable (0, 1))) return subtable;
    if ((subtable = this->find_subtable (0, 0))) return subtable;

    /* Symbol subtable. */
    if ((subtable = this->find_subtable (3, 0)))
    {
      if (symbol) *symbol = true;
      return subtable;
    }

    /* Meh. */
    return &Null (CmapSubtable);
  }

  struct accelerator_t
  {
    void init (hb_face_t *face)
    {
      this->table = hb_sanitize_context_t ().reference_table<cmap> (face);
      bool symbol;
      this->subtable = table->find_best_subtable (&symbol);
      this->subtable_uvs = &Null (CmapSubtableFormat14);
      {
	const CmapSubtable *st = table->find_subtable (0, 5);
	if (st && st->u.format == 14)
	  subtable_uvs = &st->u.format14;
      }

      this->get_glyph_data = subtable;
      if (unlikely (symbol))
      {
	this->get_glyph_funcZ = get_glyph_from_symbol<CmapSubtable>;
      } else {
	switch (subtable->u.format) {
	/* Accelerate format 4 and format 12. */
	default:
	  this->get_glyph_funcZ = get_glyph_from<CmapSubtable>;
	  break;
	case 12:
	  this->get_glyph_funcZ = get_glyph_from<CmapSubtableFormat12>;
	  break;
	case  4:
	  {
	    this->format4_accel.init (&subtable->u.format4);
	    this->get_glyph_data = &this->format4_accel;
	    this->get_glyph_funcZ = this->format4_accel.get_glyph_func;
	  }
	  break;
	}
      }
    }

    void fini () { this->table.destroy (); }

    bool get_nominal_glyph (hb_codepoint_t  unicode,
				   hb_codepoint_t *glyph) const
    {
      if (unlikely (!this->get_glyph_funcZ)) return false;
      return this->get_glyph_funcZ (this->get_glyph_data, unicode, glyph);
    }
    unsigned int get_nominal_glyphs (unsigned int count,
				     const hb_codepoint_t *first_unicode,
				     unsigned int unicode_stride,
				     hb_codepoint_t *first_glyph,
				     unsigned int glyph_stride) const
    {
      if (unlikely (!this->get_glyph_funcZ)) return 0;

      hb_cmap_get_glyph_func_t get_glyph_funcZ = this->get_glyph_funcZ;
      const void *get_glyph_data = this->get_glyph_data;

      unsigned int done;
      for (done = 0;
	   done < count && get_glyph_funcZ (get_glyph_data, *first_unicode, first_glyph);
	   done++)
      {
	first_unicode = &StructAtOffsetUnaligned<hb_codepoint_t> (first_unicode, unicode_stride);
	first_glyph = &StructAtOffsetUnaligned<hb_codepoint_t> (first_glyph, glyph_stride);
      }
      return done;
    }

    bool get_variation_glyph (hb_codepoint_t  unicode,
			      hb_codepoint_t  variation_selector,
			      hb_codepoint_t *glyph) const
    {
      switch (this->subtable_uvs->get_glyph_variant (unicode,
						     variation_selector,
						     glyph))
      {
	case GLYPH_VARIANT_NOT_FOUND:	return false;
	case GLYPH_VARIANT_FOUND:	return true;
	case GLYPH_VARIANT_USE_DEFAULT:	break;
      }

      return get_nominal_glyph (unicode, glyph);
    }

    void collect_unicodes (hb_set_t *out) const
    {
      subtable->collect_unicodes (out);
    }
    void collect_variation_selectors (hb_set_t *out) const
    {
      subtable_uvs->collect_variation_selectors (out);
    }
    void collect_variation_unicodes (hb_codepoint_t variation_selector,
				     hb_set_t *out) const
    {
      subtable_uvs->collect_variation_unicodes (variation_selector, out);
    }

    protected:
    typedef bool (*hb_cmap_get_glyph_func_t) (const void *obj,
					      hb_codepoint_t codepoint,
					      hb_codepoint_t *glyph);

    template <typename Type>
    HB_INTERNAL static bool get_glyph_from (const void *obj,
					    hb_codepoint_t codepoint,
					    hb_codepoint_t *glyph)
    {
      const Type *typed_obj = (const Type *) obj;
      return typed_obj->get_glyph (codepoint, glyph);
    }

    template <typename Type>
    HB_INTERNAL static bool get_glyph_from_symbol (const void *obj,
						   hb_codepoint_t codepoint,
						   hb_codepoint_t *glyph)
    {
      const Type *typed_obj = (const Type *) obj;
      if (likely (typed_obj->get_glyph (codepoint, glyph)))
	return true;

      if (codepoint <= 0x00FFu)
      {
	/* For symbol-encoded OpenType fonts, we duplicate the
	 * U+F000..F0FF range at U+0000..U+00FF.  That's what
	 * Windows seems to do, and that's hinted about at:
	 * https://docs.microsoft.com/en-us/typography/opentype/spec/recom
	 * under "Non-Standard (Symbol) Fonts". */
	return typed_obj->get_glyph (0xF000u + codepoint, glyph);
      }

      return false;
    }

    private:
    hb_nonnull_ptr_t<const CmapSubtable> subtable;
    hb_nonnull_ptr_t<const CmapSubtableFormat14> subtable_uvs;

    hb_cmap_get_glyph_func_t get_glyph_funcZ;
    const void *get_glyph_data;

    CmapSubtableFormat4::accelerator_t format4_accel;

    hb_blob_ptr_t<cmap> table;
  };

  protected:

  const CmapSubtable *find_subtable (unsigned int platform_id,
				     unsigned int encoding_id) const
  {
    EncodingRecord key;
    key.platformID = platform_id;
    key.encodingID = encoding_id;

    const EncodingRecord &result = encodingRecord.bsearch (key);
    if (!result.subtable)
      return nullptr;

    return &(this+result.subtable);
  }

  const EncodingRecord *find_encodingrec (unsigned int platform_id,
                                    unsigned int encoding_id) const
  {
    EncodingRecord key;
    key.platformID = platform_id;
    key.encodingID = encoding_id;

    return encodingRecord.as_array ().bsearch (key);
  }

  bool find_subtable (unsigned format) const
  {
    auto it =
    + hb_iter (encodingRecord)
    | hb_map (&EncodingRecord::subtable)
    | hb_map (hb_add (this))
    | hb_filter ([&] (const CmapSubtable& _) { return _.u.format == format; })
    ;

    return it.len ();
  }

  public:

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
		  likely (version == 0) &&
		  encodingRecord.sanitize (c, this));
  }

  protected:
  HBUINT16		version;	/* Table version number (0). */
  SortedArrayOf<EncodingRecord>
			encodingRecord;	/* Encoding tables. */
  public:
  DEFINE_SIZE_ARRAY (4, encodingRecord);
};

struct cmap_accelerator_t : cmap::accelerator_t {};

} /* namespace OT */


#endif /* HB_OT_CMAP_TABLE_HH */